The present invention relates to a new and distinct variety of nectarine tree, Prunus persica L. Batsch, which has been given the variety denomination ‘NECTASIA’. This new tree produces fruit with a long shelf life without alteration both on the tree after growth completion and after harvesting, very good eating quality, semi-clingstone yellow flesh fruit for fresh market in August or in September in the Pyrénées-Orientales department, France. Contrast is made to its parents, ‘Nectagala’ (U.S. Plant Pat. No. 17,581) yellow nectarine tree and ‘Nectachief’ (U.S. Plant Pat. No. 19,330) yellow nectarine tree, for reliable description. ‘NECTASIA’ is a promising candidate for commercial success in that it has very attractive fruits with very long shelf life without alteration before after harvesting.